(a) Field of the Invention
The present invention relates to a method for detecting broken particles in ceramic coating layer of coated fuel particles for high-temperature gas-cooled reactor.
(b) Description of the Prior Art
As a detection method of broken ceramic coating layer of coated fuel particles for high-temperature gas-cooled reactor (referred to "coated particles" for short), a method (Burn-leach method) in case of using silicon-carbide for the third coating layer which comprises burning coated particles in air to remove a carbon layer which is the fourth coating layer, thereafter boiling it in a solution of nitric acid to elute uranium and determining the uranium and a method (Mercury injection method) which comprises, after removing the fourth coating layer, that is a carbon layer, by burning, putting coated particles into mercury, applying pressure of above several tens MPa thereto from the exterior to inject mecury into the interior of broken particles and examiming the existence of mercury in the coated particles by X-ray photographing have hitherto been utilized.
However, for the present, there is not any suitable method for the detection of broken particles in case of using zirconium carbide for the coating layer.
The prior Burn-leach method has such a problem that it is necessary to burn the carbon layer of the first and second coating layers through the broken portions of silicon carbide, but, in case the broken portion is small, the first and second coating layers cannot be burned even if burning for a long time.
The mercury injection method has developed for the purpose of solving the problem in the Burn-leach method, however, the method itself is complicated besides mercury used is a poisonous material, an apparatus of generating high pressure is necessary and a X-ray generating apparatus is required.